A car is safe, comfortable, convenient, and even noble for driving compared to other traffic means. That is why a lot of people prefer to own a car. Meanwhile, with the upgraded purchasing ability, most people can afford a car now. For the consumers who drive a car, the most important thing is to safely arrive at a destination. There are many factors that have great influences on the safe driving, including the driver's energy, attention, and caution during driving, and conditions of different parts of the car. For instance, it is very important whether the tires and the braking system of the car are normal to perform their functions. A tire having an excessively low or insufficient tire pressure tends to have seriously worn tread to cause unstable gravity center of the car. On the other hand, a tire having an excessively high tire pressure tends to cause instantaneous tire blow-out while the car is moving. Both the badly worn tread and the blown-out tire are fatal to a moving car, and would endanger the driver's and the passengers' life or even other cars moving nearby the car. Therefore, the use of tire pressure warning device is no doubt necessary.
Tire pressure warning devices in the early stages can only detect an insufficient tire pressure state. The danger of an excessively high tire pressure is neglected by people in the past. Taiwanese Patent Publication No. 323600 discloses a circuit arrangement for a tire pressure warning device, which can be used to detect not only an excessively low tire pressure, but also an excessively high tire pressure.
The circuit arrangement for a tire pressure warning device according to Taiwanese Patent Publication No. 323600 includes a detecting and transmitting circuit provided in the tire pressure warning device, and a signal receiving circuit provided on a dashboard of a car. The tire pressure warning device is mounted to every tire of the car. Each of the tire pressure warning devices includes a case having a bore corresponding to an inflation valve on the tire, so that the tire pressure warning device can be mounted to the inflation valve to allow air pressure in the tire to enter the case via the bore. The detecting and transmitting circuit is provided on a printed circuit board in the case for detecting and measuring tire pressure of the tire. The tire pressure detecting and transmitting circuit includes a pressure sensing unit, a signal converter, an encoding unit, a radio converting unit, and a first power supply unit. When a measured tire pressure value is too high or too low, a radio signal is sent to the signal receiving circuit for the latter to identify the tire from which the radio signal is transmitted. The signal receiving circuit then emits an alarm to warn the driver, so that the driver can timely know the tire pressure state of every tire of the car at any time.
While the tire pressure warning device disclosed in Taiwanese Patent Publication No. 323600 is able to detect and determine whether the tire pressure is too high or too low, the radio signal representing the high or low tire pressure is obtained by comparing the detected tire pressure value with preset high and low pressure reference values. Therefore, the tire pressure warning device can only be used to detect a tire that has a tire pressure requirement matching the range between the preset high and low pressure reference values. For other tires that require higher or lower tire pressure, the tire pressure warning device is not able to correctly detect the tire pressure. As a result, the tire pressure warning device disclosed in Taiwanese Patent Publication No. 323600 can only be used on some specific tires instead of being widely used on all kinds of tires.
It is therefore tried by the inventor to develop a circuit arrangement for a tire pressure warning device and a tire pressure detecting method implemented using the tire pressure warning device with an attempt of eliminating the drawbacks in the conventional tire pressure warning devices.